For an intuitive use of a display by a user, a display to which a touch screen technology is applied has been widely used, and recently, not only a touch screen which is operated by simply touching a screen, but also a haptic function which imparts a haptic feedback to a touch screen to provide a user with a new user's experience have been developed. Here, haptic is a technology that makes a user feel the sense of touch, force, movement, and the like.
In general, the haptic technology may be implemented by converting electrical signals into mechanical energy such as vibration in a display capable of being touch-input, so that a transparent haptic film having excellent electroactivity is required to be developed.
As a material for the film having electroactivity, various electroactive polymers may be used. Examples of the electroactive polymers include a polymer such as PVDF, which uses a piezoelectric system by using a change in volume through the phase transition by voltage, or a polymer such as urethane, which uses a dielectric system in which a dielectric material shrinks and expands in a vertical direction when the dielectric material is charged.
The haptic display film is for a display, and thus basically needs to have excellent permeability and haze characteristics, and a PVDF film, which uses the piezoelectric system, has a fundamental characteristic problem in that the problem of haze caused by crystallinity after poling occurs.
Therefore, there is a need for developing a polymer film having excellent dielectric constant, modulus, and optical characteristics by using a dielectric system in which a dielectric material shrinks and expands in a vertical direction when the dielectric material is charged, and for applying the polymer film to a haptic display.